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PubMed1988

[Growth factors and embryonic development].

Embryonic development involves five major cellular events: division, migration, selective cell-cell contact, differentiation and planned cell death. Among these numerous cellular events the growth factors play a major role in regulating cell growth and differentiation by an autocrine or paracrine mechanism. The growth factors may be defined as polypeptides that stimulate cell proliferation directly through binding to specific high affinity cell membrane receptors. The best characterized group of growth factors includes the epidermal growth factor (EGF), platelet-derived growth factor (PDGF), insulin and insulin-like growth factors (IGF) and the transforming growth factors TGF alpha and TGF beta. These factors are chemically characterized by their requirement for intact disulfide bridges for biological activity and have a very broad target cell specificity. A second group of polypeptide growth factors includes fibroblast growth factors (FGF) which bind specifically to heparin and induce angiogenesis both in vivo and in vitro. Their ability to stimulate cell proliferation is mainly restricted to cells from mesodermal and neuroectodermal origin, including endothelial cells. Some very small peptides, called neuropeptide-like growth factors have been recently described. The role of these growth factors during embryogenesis is studied in vivo in mouse embryos or in Xenopus eggs or in vitro in cell cultures such as murine or human teratocarcinoma cells. Some of these growth factors such as PDGF or TGF beta are chemotactic agents, and are able to modify the extracellular matrix improving the cell migrations. For example in the Xenopus, EGF and TGF beta induce the mesoderm from the ectoderm before gastulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1980

Synthesis of retinal gangliosides during chick embryonic development.

Embryonic retina cells incorporated radioactivity from D-[6-3H]glucosamine into gangliosides in vitro. The incorporation was higher in retinas from younger embryos. The pattern of labeling of individual gangliosides of the retina changed gradually from a predominant labeling of gangliosides running chromatographically as GD3 (nomenclature of Svennerholm) and GM3 in retinas from 8-day-old embryos to a predominant labeling of those running as GD1a and GT1 in retinas from 13--18-day-old embryos and newly hatched chicks. The shift in the pattern of labeling correlated with a temporary increase of about sixfold of the activity of UDP-N-acetylgalactosamine:GM3 N-acetylgalactosaminyltransferase occurring between days 8 and 14 of embryonic development and with a regular increase of the activity of the UDP-galactose:GM2 galactosyltransferase occurring from day 8 until hatching. The activities of the CMP-NeuAc:lactosylceramide-, CMP-NeuAc:GM3-, and CMP-NeuAc:GM1-sialosyltransferases in the retinas of newly hatched chicks were 40, 20, and 40% in comparison with the corresponding activities determined in retinas of the 8-day-old embryo.

Animals↗
PubMed1991

Effect of exogenous corticosterone on chicken embryonic development.

Embryonic corticosterone (CS) levels were altered by dipping 3-day-old fertile Leghorn eggs in 0, .01, .05, and 1% CS dissolved in absolute ethanol. Mortality was determined by candling from Day 4 through hatch. Body weights and serum CS were measured daily from Day 14 until hatch. Embryos of eggs dipped in 1% CS in ethanol solution had reduced circulating CS. Embryo weights were reduced and mortality increased as concentration of hormone increased. A CS peak was observed just before hatch for control, .01 and .05% groups, but not for the .1% group. All embryos in the .1% treatment group died before hatch. The importance of embryonic CS for normal development and hatching was indicated.

Animals↗
PubMed1998

The effect of dietary protein on reproduction in the mare. VII. Embryonic development, early embryonic death, foetal losses and their relationship with serum progestagen.

Sixty-four Thoroughbred and Anglo-Arab mares aged 6-12 years were randomly allocated to 4 dietary groups and fed diets that differed in the total protein content and quality (essential amino-acids). Forty mares were non-lactating and 24 lactating. Eight mares were withdrawn from the investigation owing to injuries or gynaecological pathology. An overall conception rate of 94.6% and a foaling rate of 80% was achieved. Five of 14 (35.7%) mares (Group 1) fed a low-quality protein diet suffered from early embryonic loss before 90 days of pregnancy compared to 3 of 41 (7.3%) mares in the remaining groups that received the higher-quality protein in their diets. Serum progestagen concentrations of mares in Group 1 that suffered foetal loss were indicative of luteal function insufficiency during the 1st 40 days post-ovulation. Non-lactating mares in all 4 groups gained on average approximately 30 kg in mass during the 90 days before the breeding period. Lactating mares in Group 1 (low-quality protein) lost on average 25 kg in mass during lactation, with no weight loss observed among the lactating mares in the other 3 groups. No difference in the diameter of the embryonic vesicle was found between dietary groups until Day 35 of pregnancy.

Animals↗
PubMed1997

Expression of chicken hepatic type I and type III iodothyronine deiodinases during embryonic development.

In embryonic chicken liver (ECL) two types of iodothyronine deiodinases are expressed: D1 and D3. D1 catalyzes the activation as well as the inactivation of thyroid hormone by outer and inner ring deiodination, respectively. D3 only catalyzes inner ring deiodination. D1 and D3 have been cloned from mammals and amphibians and shown to contain a selenocysteine (Sec) residue. We characterized chicken D1 and D3 complementary DNAs (cDNAs) and studied the expression of hepatic D1 and D3 messenger RNAs (mRNAs) during embryonic development. Oligonucleotides based on two amino acid sequences strongly conserved in the different deiodinases (NFGSCTSecP and YIEEAH) were used for reverse transcription-PCR of poly(A+) RNA isolated from embryonic day 17 (E17) chicken liver, resulting in the amplification of two 117-bp DNA fragments. Screening of an E17 chicken liver cDNA library with these probes led to the isolation of two cDNA clones, ECL1711 and ECL1715. The ECL1711 clone was 1360 bp long and lacked a translation start site. Sequence alignment showed that it shared highest sequence identity with D1s from other vertebrates and that the coding sequence probably lacked the first five nucleotides. An ATG start codon was engineered by site-directed mutagenesis, generating a mutant (ECL1711M) with four additional codons (coding for MGTR). The open reading frame of ECL1711M coded for a 249-amino acid protein showing 58-62% identity with mammalian D1s. An in-frame TGA codon was located at position 127, which is translated as Sec in the presence ofa Sec insertion sequence (SECIS) identified in the 3'-untranslated region. Enzyme activity expressed in COS-1 cells by transfection with ECL1711M showed the same catalytic, substrate, and inhibitor specificities as native chicken D1. The ECL1715 clone was 1366 bp long and also lacked a translation start site. Sequence alignment showed that it was most homologous with D3 from other species and that the coding sequence lacked approximately the first 46 nucleotides. The deduced amino acid sequence showed 62-72% identity with the D3 sequences from other species, including a putative Sec residue at a corresponding position. The 3'-untranslated region of ECL1715 also contained a SECIS element. These results indicate that ECL1711 and ECL1715 are near-full-length cDNA clones for chicken D1 and D3 selenoproteins, respectively. The ontogeny of D1 and D3 expression in chicken liver was studied between E14 and 1 day after hatching (C1). D1 activity showed a gradual increase from E14 until C1, whereas D1 mRNA level remained relatively constant. D3 activity and mRNA level were highly significantly correlated, showing an increase from E14 to E17 and a strong decrease thereafter. These results suggest that the regulation of chicken hepatic D3 expression during embryonic development occurs predominantly at the pretranslational level.

Amino Acid Sequence↗
PubMed1996

Investigation of developing embryonic morphology using optical coherence tomography.

Improved imaging of morphological changes has the potential of offering new insight into the complex process of embryonic development. Optical coherence tomography (OCT) is a new imaging technique for performing in vivo cross-sectional imaging of architectural morphology by measuring backscattered infrared light. This study investigates the application of OCT for imaging developing structure in Rana pipiens, Xenopus laevis, and Brachydanio rerio. Images are compared to conventional histological baselines. Cross-sectional imaging can be performed and structural morphology identified at greater imaging depths than possible with confocal and light microscopy. Repeated OCT imaging may be performed in vivo in order to track structural changes throughout development.

Animals↗
PubMed1986

Changes in insulin binding to developing embryonic chick neural retina cells.

Specific cell surface insulin binding to embryonic chick neural retina cells has been demonstrated in vivo. Kinetics of insulin binding as well as hormonal specificity were similar to those reported for other vertebrate cells and tissues, both neural and nonneural. When surface insulin binding to retinal cells was studied as a function of embryonic age, a developmental relationship was observed. Scatchard analysis revealed that the number of cell surface insulin receptors decreased approximately 75% between days 10 and 16 of embryonic development. Receptor affinities remained fairly constant for this period.

Animals↗
PubMed1983

The embryonic development of ear-tufts and associated structural head and neck abnormalities of the Araucana fowl.

Developing embryonic structural abnormalities of ear-tufted embryos of the Araucana fowl are described. These abnormal structures are peduncle, cleft, ear opening, tympanic membrane, and columella auris. The structural abnormalities are believed to be due to the early incomplete fusion of the hyoid and mandibular arches from the distal part of the ear opening to the neck area.

Animals↗
PubMed1989

Extracellular matrix, cell skeletons, and embryonic development.

During embryonic development, the extracellular matrix (ECM) promotes the production of differentiated products by epithelial cells and the migration of mesenchymal cells, and probably also plays a role in epithelial-mesenchymal transformation. Here we examine the role of the cell skeleton (actin, microtubules, intermediate filaments) in mediating matrix effects on mesenchymal cell morphology, migration, and formation. The interaction of both epithelial cells and mesenchymal cells with ECM seems to involve the actin cortex, which is best developed in the base of the epithelial cell, where it attaches to underlying matrix via membrane-intercalated receptors. To interact with the matrix, the fibroblast has appropriate ECM receptors and an actin cortex around the whole cell. The actin cortex is absolutely required for assumption of bipolar shape, elongation, and movement through the matrix. Since the cortex seems to be anchored to the matrix, it is unlikely that it moves during cell migration. A new hypothesis states that the microtubule- and intermediate filament-rich endoplasm, containing the nucleus, moves past the actin cortex-receptor-matrix complex into the newly synthesized front end of the mesenchymal cell to effect forward movement. When epithelial cells transform into mesenchyme in the embryo, or when they are induced to do this in vitro, they switch from the keratin intermediate filament profile to one rich in vimentin, and the effect of cell matrix interaction on cell shape is profoundly altered. Vimentin-actin interactions with ECM may be a major factor in the ability of a cell to become mesenchymal.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2000

Diagnosis and management of abnormal embryonic development characterized by formation of an embryonic vesicle without an embryo in mares.

OBJECTIVE: To determine the incidence, ultrasonographic characteristics, and risk factors associated with embryonic development characterized by formation of an embryonic vesicle without an embryo in mares. DESIGN: Prevalence survey. ANIMALS: 159 pregnant mares. PROCEDURES: From 1994 to 1998, mares between 11 and 40 days after ovulation with normal and abnormal embryonic development were examined ultrasonographically, and characteristics of each conceptus were recorded. RESULTS: The incidence of abnormal embryonic development in mares characterized by formation of an embryonic vesicle without an embryo was 7/159 (4.4%) during the 5 breeding seasons. Age and breed of mare or type of semen used did not differ for mares with normal and abnormal embryonic development. The percentage of mares in which the conceptus was undersized during > or = 1 examination was significantly higher for mares with abnormal conceptuses (5/7), compared with mares with normal conceptuses (2/147; 1.4%). The percentage of examinations during which the conceptus was undersized was significantly higher for abnormal conceptuses (12/27; 44.4%), compared with normal conceptuses (4/448; 0.9%). CONCLUSIONS AND CLINICAL RELEVANCE: To diagnose an embryonic vesicle without an embryo, mares should be examined by use of transrectal ultrasonography on day 25 after ovulation. When an embryo cannot be identified at that time, mares should be reexamined at intervals of 1 to 3 days until day 30. Because undersized conceptuses are more likely to be abnormal, development of undersized conceptuses should be monitored closely.

Animals↗
PubMed2006

Tenectin, a novel extracellular matrix protein expressed during Drosophila melanogaster embryonic development.

During Drosophila embryonic development, various morphogenetic processes require the remodeling of the extracellular matrix. In a previous study, we have identified and characterized a cDNA encoding a novel putative extracellular matrix protein named tenebrin, in the beetle Tenebrio molitor. Here, we examine the expression of the Drosophila ortholog, referred to as Tenectin (Tnc), during embryonic development. Tnc is expressed in the majority of tissues of neuroectodermic origin such as hindgut, foregut, tracheal system, anal plate, and CNS. In the CNS, the Tnc transcript is restricted to a few cells, whereas the protein is located in the dorsal part of the axonal tracts. In the hindgut and the trachea, Tnc protein is expressed on the apical pole of the cells. Tnc is an extracellular matrix protein secreted in a polarized way in different organs of Drosophila embryos.

Animals↗
PubMed1996

Embryonic development of Schwann cells: multiple roles for neuregulins along the pathway.

During the past few years important advances have been realized in the understanding of the molecular and cellular mechanisms operating in the differentiation of Schwann cells from neural crest cells. In particular the development of in vitro culture systems has allowed the analysis of commitment to the Schwann cell lineage, identification of an intermediate between the neural crest cell and the Schwann cell, and initial analysis of the factors controlling determination and differentiation processes. These studies point in particular to major roles for neuregulins which appear to be involved in the control of cell survival, proliferation, and differentiation, as well as of gene expression at different levels of the pathway.

Animals↗
PubMed1983

Regulation of the expression of genes encoding types I, II, and III collagen during chick embryonic development.

During the embryonic development of the chicken, stimulation of production of collagen-enriched tissue such as bone matrix, cartilage matrix, and skin dermis occurs between day 7 and day 15. We have examined the levels of the RNAs encoding the interstitial collagens (types I, II, and III) to determine if this developmental progress is associated with increased accumulation of collagen RNA. Using cell-free translation and DNA:RNA hybridization techniques, we have detected a coordinate enhancement of approximately 10-fold in the steady state levels of whole embryo RNAs encoding the alpha 1(I), alpha 2(I), alpha 1(II), and alpha 1(III) collagens between 5 and 10 days of chick embryonic development. The developmental pattern of expression of these collagen genes in whole embryos is in marked contrast to that of two noncollagenous proteins, cellular fibronectin and beta-actin, whose RNA levels were not found to change dramatically during early chicken development. In addition, we have observed that at least 3 of the 4 collagen genes examined were expressed at low levels beginning between 1-2 days. Both 5'- and 3'-specific alpha 2(I) collagen gene DNA probes hybridized to early stage and late stage chick embryo RNAs of identical sizes. DNase I-hypersensitive sites have been detected near the 5' end of the alpha 2(I) collagen gene in chromatin isolated from both 2-day and 5-day embryos, representing developmental time points well before and at the threshold of the onset of enhanced collagen RNA synthesis, respectively. These results suggest that the same gene is expressed in early and late chick embryos to yield alpha 2(I) collagen RNAs of similar structure.

Animals↗
PubMed1999

Extracellular modulation of the Hedgehog, Wnt and TGF-beta signalling pathways during embryonic development.

Localized embryonic expression of members of the Hedgehog, Wnt and TGF-beta families of secreted factors has been shown to organize pattern and provide positional information in many developing systems. Recently, several extracellular factors have been described that act either as facilitators or inhibitors of the activities of those secreted proteins. The variety of molecular strategies involved in the extracellular modulation of signalling activities in the embryo underscores the importance of maintaining a tight spatial and temporal control of the activities of organizing centers during development.

Animals↗
PubMed1991

Distribution and expression of two interactive extracellular matrix proteins, cytotactin and cytotactin-binding proteoglycan, during development of Xenopus laevis. I. Embryonic development.

An immunohistochemical study of the localization of cytotactin and cytotactin-binding (CTB) proteoglycan throughout embryonic development of the anuran Xenopus laevis reveals that both appear in a restricted pattern related to specific morphogenetic events. CTB proteoglycan expression is first detected during gastrulation at the blastopore lip. Later, it is seen in the archenteron roof around groups of cells forming the notochord, somites and neural plate. Cytotactin first appears after neurulation, and is restricted to the intersomitic regions. Both molecules appear along the migratory pathways of neural crest cells in the trunk and tail. Later, cytotactin is present at sites where neural crest cells differentiate, around the aorta and in the smooth muscle coat of the gut; CTB proteoglycan is absent from these sites. In the head, cytotactin is initially restricted to the regions between cranial somites, while CTB proteoglycan is distributed throughout the cranial mesenchyme. The expression of both molecules is later associated with key events in chondrogenesis during the development of the skull. After chondrogenesis, CTB proteoglycan is distributed throughout the cartilage matrix, while cytotactin is restricted to a thin perichondrial deposit. Both molecules are expressed in developing brain. These findings are compared to studies of the chick embryo and although distinct anatomical differences exist between frog and chick, the expression of these molecules is associated with similar developmental processes in both species. These include mesoderm segmentation, neural crest cell migration and differentiation, cartilage development, and central nervous system histogenesis.

Animals↗
PubMed1992

Effects of three methods of selection for litter size in mice on pre-implantation embryonic development.

Characteristics of preimplantation embryonic development to Day 3.5 of gestation were evaluated in lines of mice after 21 generations of selection for litter size or components of litter size. Selection criteria were direct selection for number born (LS), selection on an index of ovulation rate and the proportion of ova shed that resulted in fully formed pups (IX), selection for number born in unilaterally ovariectomized females as an indication of uterine capacity (UT), and an unselected control (LC). Comparison of the average distributions of embryonic stage of development on the left side of the uterus showed that selection (average effect of LS, IX, and UT vs. LC) tended to advance (p = 0.07) the average stage of embryonic development at Day 3.5 and shift the distribution (p = 0.10) by increasing the frequency of expanded blastocysts and decreasing the frequency of pre-morula embryos. A similar shift in the distribution on the right side of the uterus was not statistically significant. Selection decreased (p = 0.06) variability in developmental stage among embryos within the right uterine horn. These selection criteria evaluated in the mouse appear to have changed the frequencies of genes that affect some determinants of average stage of embryonic development and uniformity of development within a uterine horn at Day 3.5 of gestation.

Animals↗